Both the second and third man will always know what color they are wearing.

If 4 sees two of the same color, he calls it out. Three and two both know they have the opposite color and shout it out. On hears what they say and shouts the same color as 4.

Now if 4 sees two different colors, he is unsure and waits. Three knowing that 4 would shout out the answer immediately if he saw two of the same color, shouts out the opposite color of what two is wearing. Two realizes that he is wearing the opposite of three and shouts that color out. If an incorrect response killed only the incorrect guesser, then at least one of the remaining two would live. If one of them guesses wrong, they die, then the other says the same color and lives. If the first guesses chooses correctly, the last man says the opposite color and everyone lives!